Electrical circuits



c. W; HANsEL 1,999,190

ELECTRICAL CIRCUITS Filed on. 51, 1932 Z'Sheets-Sheet l $00M: 0/ mm 00 r/zmuzA/cr Mam/r50 Irma;

INVENTOR- c. ANSELL.

' BY M ATTORNEY- A ril 30,1935." c. w-. HANSELL ELECTRICAL CIRCUITS Filed Oct. :51, 1952 2 sheets sheet 2 INVENTOR- c.w. HA? SELL 'ATFORNEY- n'uounu'ou Patented Apr. so, 1935 1,999,190

UNITED STATES PATENT. OFFICE,

ELECTRICAL CIRCUITS 4 Clarence W. Hansel], Port Jefierson, N. Y., assignor to Radio Corporation of America, a corporation of Delaware Application October 31, 1932, Serial No. 640,370

8 Claims. (Cl. 250-17) This invention relates to apparatus for elimi- 22 negative grid biasing potential for vacuum nating undesired amplitude variations in the outtubes 8, Ill. The filaments or cathodes of the put circuits of, for example, phase and frequency tubes 8, ID are energized to an electron emitting modulated transmitters. condition with alternating-currents through the In practice, the power amplifiers used in phase action of transformers 24, 26. 5 p

and frequency modulation transmitters, intro- Due to fluctuations in the plate potential supduce ripples or undesired amplitude variations in plied through lead 28, aswell as fluctuations in the final output to be transmitted. These variagrid bias supplied through conductor 20, as well 'tions arise chiefly from the use of alternating curas variations in filament voltage and current be- 10 rent to heat the filaments of the poweramplifiers cause of their energization to an electron emit- 10 and from ripple in the negative bias voltage and ting condition with alternating currents, it will plate potential when derived from rectifiers or a be found that the high frequency phase or frecommutator type of generator. quency modulated. energy in the output circuit The principal object of my present invention l2 will .also have an undesired ripple or ampliis to provide a method and means for eliminating tude variation. To eliminate this undesired am 15 these undesired amplitude variations. Briefly, to plitude variation to the output circuit l2 do so, a portion of the amplifier output is rectithere is coupled a diode rectifier 30 by means of fied so as to obtain waves which are a copy of any an induction coil 32. The rectifier is by-passed undesired ripple or amplitude variation in the for high frequencycurrentsby means of byamplifier output circuit. This wave copy is then passing condenser 34. The output of the rec- 20 applied to the amplifier in such a way as to modutifier will be a copy of the undesired amplitude late its output in reverse sense whereby the introvariation or ripple appearing in the output cirduced modulation effectively balances out nearly cuit l2, and this wave copy is applied through all of the undesired amplitude changes. variable tap 32 to resistor 22 in such a way as v 25 My present invention'is more fully described to vary the grid bias or, in other words, modulate 25 hereinafter with the aid of the accompanying the'power amplifiers 8, ill in such a direction as drawings, wherein, to balance out the undesired ripple in the output Figure lis a wiring diagram of a phase or fre circuit l2. quency modulation transmitter havingincorpo- In the arrangement shown in Figure 2, the

rated therein an arrangement according to my rectifier 2 supplies the cascaded amplifier 30 present invention for eliminating undesired amstages with anode potential through conductors plitude variation due to fluctuations in power 28. The cascaded amplifi 44 are prefsupply for the power amplifier; erably of the pushpull type although they need Figure 2 is a modification of the arrangement not be limited thereto. The filament heating shown in Figure -1 wherein correcting modulation current sources for the cathodes of the stages 42,, 35 is applied to an early stage of a plurality of cas- 44 have not been shown, but may be either altercaded amplifiers; and, nating current circuits, or direct current cir- Figure 3 is a further modification wherein corcuits, and also, the grid biasing potentials need recting potentials are applied to the screen grids not be derived from an A. C. source, but, the of a power amplifier to eliminate from a phase grid polarizing arrangement may be of the self- 40 or frequency modulated transmitter undesired biasing type such as a grid leak resistor 46 of amplitude variations. I the pushpull cross-neutralized stage 44, or, the Turning to Figure 1, a source of frequency or grid biasing potential may be derived from a phase modulated waves 2 energizes through constant source of potential such as battery 48 transmission line 4 and tunablev input circuit 6, app y bias ou resistor 50 o t e 45 pushpull connected electron discharge devices grids of the tubes forming amplifier 40. or vacuum tube amplifiers 8, ID. The amplifier To eliminate undesired amplitude variation in tubes 8, II] are cross-neutralized as shown, to the final output circuit 52 of amplifier 44, a porprevent parasitic oscillation generation and are tion ofthe output is rect fi y rectifier and .50 provided with a tunable output circuit l2 in turn fed through conductors 54, 56 to the grid biasing 5O energizing a radiating antenna l4. circuit 48, 50 for the grids of the tubes forming Anode potential for tubes 8, I0 is supplied from ampl fie 0. y adj the direction and rectifier unit l6 energized 'with commercial so magnitude of applied rectified waves from recticycle current from transformer Ill. The rectifier fier 30 to the grids of tubes 40, the energy in the 55 unit 16 also supplies through lead 20 and resistor output circuit 52 will be modulated in a reverse sense so as to substantially balance out the undesired ripple or amplitude variations normally present. Consequently, energy radiated over antenna 14 will be of substantially constant am plitude and modulated in frequency or in phase dependent upon the character of modulation source 2.

If desired, I may, of course, connect rectifier 30 of both Figures 1 and 2 in series with the negative biasing source to the grids of the amplifier tubes. connect a resistance of suitable value across the D. C. output of rectifier 30 to permit the passage of rectified grid current in opposition to the rectifier.

It is not necessary that'the correcting potentials be applied to the usual control electrodes or grids of an electron discharge device amplifier. As shown in Figure 3, rectifier 30 coupled to the output circuit l2 of pushpull connected screen grid electron discharge devices 60, G2 feeds through conductors 64, 66 a replica of the amplitude variations appearing in circuit I! to the screen grid voltage dropping resistor 68. Consequently, the screen grids 10, 12 grounded by means of radio frequency by-passing condenser '14 will be subjected to potentials which will balance out or cause the cancellation of un desired amplitude ripple appearing in the output circuit l2. In this case also I may connect rectifier 30 in series with the resistor 68, as an alternative arrangement.

Having thus described my invention, what I claim is:

1. In electrical apparatus forreducing power supply noise, an amplifier comprising an electron discharge device having an anode a cathode and a control electrode, an input circuit coupled to said control electrode, an output circuit connected to said anode, a source of modulated electrical waves coupled to said input circuit, a rectifier coupled to the output circuit of said amplifier for deriving the amplitude component from said modulated waves, and, a circuit coupled to the input circuit of said amplifier and to the output of said rectifier for impressing on the energy in said amplifier compensating energy from said rectifier whereby the output of said amplifier is a modulated wave substantially free of all amplitude variations.

2. In combination, a source of modulated electrical waves, an amplifier" amplifying energies from said source, said amplifier producing amplitude variations in the amplified output thereof, a rectifier coupled to the output circuit of said amplifier for deriving therefrom a copy of all of the amplitude variations in said modulated waves, and, a circuit for applying the wave copy to said amplifier in such a way'as to in the output circuit of said amplifier.

3. In combination, a source of modulated waves, an electron discharge device amplifier coupled to said source for amplifying waves from said source, said amplifier comprising an elec-' tron discharge device having an anode a-cathode and a control electrode, an output circuit for said amplifier, a rectifier coupled to the output circuit of said amplifier for deriving therefrom waves corresponding to all amplitude variations in the output circuit of said ampli- In this case it is preferable to- .fier, and, a circuit for applying the'output wave energy of said rectifier to the control electrode of said amplifier whereby all amplitude variations in the output circuit of said amplifier are substantially eliminated.

4. In combination, a source of phase or frequency modulated waves, an amplifier for amplifying the phase or frequency modulated waves, said amplifier producing undesired amplitude variations in the amplified waves, a rectifier rectifying a portion of the amplified waves to obtain a copy of all amplitude variations in the amplified waves, and a circuit for applying the wave copy to the amplifier in such a way as to balance or neutralize substantially all of the amplitude variations introduced by the amplifier.

-'5. In electrical apparatus for reducing power supply noise, an amplifier comprising an electron discharge device having an anode, a cathode, a screen-like electrode and a control electrode, an input circuit coupled to said control electrode, an output circuit connected to said anode, a source of modulated electrical waves coupled to said input circuit, a rectifier inductively coupled to the output circuit of said amplifier for deriving the amplitude component from said modulated waves, and, a circuit coupled to the screen-like electrode in said amplifier and to said rectifier for combining with the wave energy in said amplifier compensating energy from said rectifier whereby the output of said amplifier is a modulated wave substantially free of all amplitude variations.

6. In combination, a source of modulated electrical waves, an amplifier amplifying energies from said source, said amplifier producing amplitude variations in the amplified output thereof, a rectifier inductively coupled to the output circuit of said amplifier for deriving therefrom a copy of all of the amplitude variations in said modulated waves, and, a circuit for applying the wave copy to said amplifier in such a way as to eradicate substantially all amplitude variations in the output circuit of said amplifier.

7. In combination, a source of modulated waves, an electron discharge device amplifier coupled to said source for amplifying waves from said source, said amplifier comprising an electron discharge device having an anode a cathode and a control electrode, an output circuit for said amplifier, a rectifier inductively coupled to the output circuit of said amplifier for deriving therefrom waves corresponding to all amplitude variations in the output circuit of said amplifier, and, a circuit for applying the output wave energy of said rectifier to the control electrode of said amplifier whereby all amplitude variations in the output circuit of said amplifier are substantially eliminated.

.eradicate substantially all amplitude variations/ In combination a source of phase or quency modulated waves, an amplifier for amplifying the phase or frequency modulated waves, said amplifier producing undesired amplitude variations in the amplified waves, a rectifier, inductively coupled to said amplifier, rectifying a portion of the amplified waves to obtain a copy of all amplitude variations in the amplified waves, and a circuit for applying the wave copy to the amplifier in such a way as to balance or neutralize substantially all of the amplitude variations introduced by the amplifier.

CLARENCE W. HANSELL.

III 

